1. Field of Invention
The present invention relates broadly to tamper-evident fastening devices. More particularly the invention relates to a threaded fastener such as a screw or drain plug with a tamper-evident sheath formed from a thermoshrinkable sleeve.
2. Background of Invention
Many mechanical devices contain screw-type plugs in critical functions. One such example is the oil drain plug of motors. Lube and oil change businesses incur considerable expense every year replacing or repairing motors in vehicles where a loose oil plug has led to loss of oil and failure of the motor. The loose state of the oil plug may be the result of deliberate tampering or improper maintenance by service personnel.
Given the importance of the function of these types of fasteners, it is highly desirable to have a convenient device and/or method for detecting removal or tampering. Additionally, it is desirable to have an efficient means to monitor servicing of these devices that would verify proper maintenance and installation for the purpose of quality control.
Currently, a method in common use is spraying across the device with spray paint. This method suffers the disadvantages of being easy to circumvent by one intent on deceit. This method also results in disfiguration of the equipment with splotches of spray paint and can cause confusion after multiple servicing events in which multiple layers of paint have been applied.
Thus, there is a need for a tamper-evident fastening device that can be used as a motor oil drain plug to monitor proper installation and unauthorized manipulation of such plugs.